Make sure we populate the initroot filesystem late enough

[Benjamin Herrenschmidt]

> It's most likely a red herring, lots of config changes
> make the bug go away on some kernel versions (but not
> on others); the problem is very sensitive to changes in
> memory layout.

I wouldn't be that sure ... I've had problems in the past with PMU based
cpufreq... looks like flushing all caches and hard-resetting the
processor on the fly when there can be pending DMAs might be a source of
trouble... especially on CPUs that don't have working cache flush HW
assist.

Ben.